With respect to optical communications components and the like, conventional card guide assemblies are primarily designed for circuit pack guidance into a shelf or chassis. These card guide assemblies are not readily applicable at the circuit pack level, where guidance for pluggable electro-optic modules, such as small-form factor pluggable electro-optic modules, is required. For example, the card guide assemblies are typically designed to mount through the board when utilized at the circuit pack level and require some sort of mounting bracket, such as a fastener or clip, for this reason. As a result, the card guide assemblies are board thickness-dependent. The holes created in the board increase the routing complexity of the board by blocking circuit signal routing channels in the board and negatively impact the availability of the bottom of the board for the placement of components.
The current state-of-the-art for cooling most pluggable electro-optic modules involves mounting heatsinks directly to the components requiring cooling using various mounting brackets and/or adhesives. Most industry-standard XFP type electro-optic modules that plug into a cage assembly are cooled using clip-on heatsinks or the like, and do not use card guide assemblies. The interface is a sliding dry contact interface and the heatsinks cool the components through the convection cooling of the entire circuit pack when it is plugged into the electronic shelf of the system. The current state-of-the-art is limited in its ability to transfer all of the heat present when the circuit pack is plugged into the electronic shelf of the system, however, because, when multiple pluggable electro-optic modules are plugged into the circuit pack, the heatsinks that are located downstream of the incoming air flow are blocked and starved of air flow from the heatsinks that are located upstream. This negatively limits the number of pluggable electro-optic modules that can be plugged into the circuit pack. This is true for both cage-less and cage-mounted XFP type electro-optic modules.